Tip

All Enhanced IGRP internal routes have an administrative distance of 90, and place D in front of them to indicate that they are Enhanced IGRP internal routes.

IGRP routes with the same autonomous system number as Enhanced IGRP are automatically redistributed into Enhanced IGRP. For the Enhanced IGRP routing process, IGRP routes are treated as external. When IGRP routes are propagated into Enhanced IGRP, the metric value of IGRP is multiplied by 256. This automatic redistribution does not cause a routing loop, although IGRP has an administrative distance of 100, and external Enhanced IGRP has an administrative distance of 170.

Before the routes are installed into the routing table, the metric of the routes is compared and the metric conversion is performed by multiplying with 256. The lower of the two metrics is selected and installed into the routing table.

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